DNA Protection Protein, a Novel Mechanism of Radiation Tolerance: Lessons from Tardigrades

Abstract

Genomic DNA stores all genetic information and is indispensable for maintenance of normal cellular activity and propagation. Radiation causes severe DNA lesions, including double-strand breaks, and leads to genome instability and even lethality. Regardless of the toxicity of radiation, some organisms exhibit extraordinary tolerance against radiation. These organisms are supposed to possess special mechanisms to mitigate radiation-induced DNA damages. Extensive study using radiotolerant bacteria suggested that effective protection of proteins and enhanced DNA repair system play important roles in tolerability against high-dose radiation. Recent studies using an extremotolerant animal, the tardigrade, provides new evidence that a tardigrade-unique DNA-associating protein, termed Dsup, suppresses the occurrence of DNA breaks by radiation in human-cultured cells. In this review, we provide a brief summary of the current knowledge on extremely radiotolerant animals, and present novel insights from the tardigrade research, which expand our understanding on molecular mechanism of exceptional radio-tolerability.

Effect of Clinical X-rays on Methicillin-resistant Staphylococcus aureus and Other Bacterial Isolates from Radiology Equipment

“…The possible explanation for the non-relativeness between an isolates' antibiotics resistance and its X-ray irradiation resistance can be attributed to their mode of attack. Antibiotics are tailored to be target specific on sites/organelles of organism or group of organisms while clinical X-ray radiations are not but result to oxidative stress [9,32].…”

“…This is because clinical xrays which are designated human-tolerable are engineered to attenuate the adverse biological effects of their radiation on living cells [4,33]. Secondly, prokaryotes are known to exhibit much higher radiation tolerance than animals and humans [9]. As a result, the genotype profile of the cells may have been preserved using some form of reversion mechanism (such as base and nucleotide excision repair) [10,12] or defense mechanisms (catalase and superoxide dismutase synthesis) [13] thereby protecting the cells.…”

“…The inability of the isolate to synthesize and secrete catalase enzyme to resist the oxidative stress induced by X-ray exposures may be responsible for the cell death [13]. Unlike the other isolates which were able to withstand the oxidative stress from the prokaryotes are known to exhibit much higher mals and humans [9]. As a result, the genotype profile of the cells may have been preserved using some form of reversion mechanism (such as base and nucleotide excision repair) [10,12] or defense mechanisms (catalase and superoxide ] thereby protecting the isolate from X-ray highest survival level to high X-ray S. aureus isolate from mammogram unit.…”

“…They are continually exposed to varying exposure doses. Surprisingly, some of these pathogens are not killed by these refracted beams of radiation, instead they gradually buildup résistance and adapts to the environmental and oxidative stress build up due to these radiation [9].…”

Space Radiation Biology for “Living in Space”

“…A recent in vitro study also confirmed that Dsup can protect chromatin DNA from hydroxyl radicals [252]. Currently, a Dsup homolog has only been found in another tardigrade species, Hypsibius exemplaris, which belongs to the same taxonomic family of R. varieornatus [252][253][254]. These findings indicate that tardigrades have evolved their own stress-resistant machinery in their lineages and such unique machinery can also function in human cells.…”